In the manufacture of incandescent lamps the heating of metals and metallic alloys and compounds within the assembled and sealed lamp has long been employed to remove contaminants from the partial vacuum or other gaseous fill sealed within the lamp envelope. The contaminants occur in the atmosphere within the envelope and during a manufacturing flashing process are boiled from the incandescent lamp filament and its supporting lead wires. After flashing and during lamp burning additional contaminants appear which prior gettering methods do not efficiently remove from the lamp.
For example R. K. Braunsdorf, in U.S. Pat. No. 2,489,261, describes a zirconium family getter wire connected across the filament support wires. Simultaneously with flashing of the filament by supplying current through the support wires the getter wire is brought to incandescence, avoiding volatilization, and fused to small balls. Continued gettering is attributed to the fused balls but their active surface is minimized by their spherical shape. Similarly in U.S. Pat. No. 2,913,277 to R. H. Atkinson a gettering strip is resistively heated to below its melting point and melted to residual small bodies at their original site, avoiding volatilization. No subsequent gettering is attributed to the residual getter material.
Accordingly the object of the present invention is to provide a lamp as an intermediate and as a final product, and a method of treating the lamp which affords improved gettering action at the time of lamp flashing and substantially larger gettering areas during the operating life of the lamp.